The present invention relates to spray guns for applying coatings, and, in particular to air controls for high volume, low pressure (HVLP) spray guns. HVLP guns are commonly used to apply finish coats to painted or varnished products. As such, it is desirable that the coating be applied in an even and consistent manner. HVLP guns use air supplied by an external turbine to apply a fluid coating that hardens into a finish. Specifically, the HVLP gun is provided with a container for storing the fluid coating, while the external turbine supplies pressurized air to the gun to pressurize the container and to provide an atomization air jet in which the pressurized fluid is sprayed. A check valve is positioned between the container and the gun to prevent fluid from migrating backward into the gun after the pressure in the container drops. Conventional check valves are connected to a pressure line connecting the container with the gun. For example, a duckbill check valve, which comprises a rubber tube having a flat end, is positioned inside of the container where the pressure line enters. Duckbill check valves, however, produce pressure loss in the pressure line, which is particularly undesirable in low pressure spray guns. Also, duckbill check valves are quite easily clogged, requiring frequent replacement and disassembly of the spray gun container. Other check valve designs are incorporated into the pressure line outside of the container. Such check valves, however, produce significant pressure drops in addition to being small and difficult to clean. There is, therefore, a need for an improved check valve for use in HVLP spray guns.